Brush holder



Patented Aug. 16, 1949 BRUSH HOLDER Gerhard P. Lessmann, Pittsburgh, Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application November 6, 1947, Serial No. 784,362

2 Claims. (01. 171-324) My invention relates to brushholders, particularly those which are designed for use in directcurrent dynamo-electric machines.

The object of my invention is to provide a brushholder which is cheaper to make than any corresponding brushholder of the prior art.

More specifically, an object of my invention is to provide a brushholder which is adapted to be made as a casting from a permanent mould, by which is meant a steel or metal mould as distinguished from a sand mould.

Still more specifically, my invention relates to a hollow brushholder which is designed to use the least number of cores in the mould, all cores being capable of being inserted and withdrawn in one direction at one time, which is a considerable departure from past practices, which have, in many instances, required cores to be withdrawn in three or more different directions.

With the above and other objects in view, my invention consists in the structures, assemblies, combinations, parts and methods of design and operation hereinafter described and claimed, and illustrated in the accompanying drawing, wherein Fig. 1 is a plan View of the brushholder casting, and Fig. 2 is a sectional view of the brushholder casting, approximately on the plane indicated by the line II-II of Fig. l, with the pressure-finger, spring, and brushes being shown in elevation, to make up a more or less complete assembly.

The brushholder proper is shown at 3, It is a hollow casting which is adapted to be made from a permanent mould (not shown) and. requiring cores (not shown) which may all be inserted and withdrawn in one direction at one time. It is characterized by having a plurality of brushboxes 4 which are designed for holding brushes 5 which bear on a commutator 5. The brush-boxes 4 have Walls which extend substantially in the direction in which the cores (not shown) are to be moved when being inserted and withdrawn into and out of the mould (not shown). As the description proceeds, it will be seen that it is necessary to refer to this direction, from time to time, in order to describe the planes of the various surfaces which are provided on the hollow brushholder. Thus, the purposes of my invention will be served by any surface which is substantially parallel with this direction, or which is so inclined thereto that the core which forms said surface can be withdrawn from above, by being withdrawn in the direction of core-insertion and. withdrawal.

The hollow brushholder casting has a rear mounting-wall I which has a rear surface 8 at an angle to said direction of core-insertion and withdrawal, this rear-surface being formed by the shape of the mould, and not by the core, as will be readily understood, The mounting-wall I has a. thickened mounting-pad portion 10 which is formed as a protuberance on the inner side of the wall, and the lower inner surface ll of this mounting-pad portion lies in such direction as to admit of said core-insertion and withdrawal, being illustrated as being parallel to said direction, although it might be inclined at an angle thereto, as above explained, at the expense of requiring a trifle more material in the casting. The thickened mounting-pad portion In of the mountingwall 7 has a tapped hole 12 therein, for receiving a mounting-bolt (not shown) for supporting the brushholder. In accordance with known practices of the casting art, this hole I2, which requires tapping for the use of a bolt, is produced by a tapped steel insert l3 which is located in the mould and cast into the metal during the casting process. This can be done with great accuracy and eliminates drilling and tapping the finished brushholder.

The mounting-wall 1 also has an upper thickened lip-portion l4, which is formed as a protuberance on the inner surface of the mountingwall 1, at the top of the wall. This lip-portion 14 has an inner surface l5 which lies in substantially the previously mentioned direction of coreinsertion and withdrawal, that is, which is substantially parallel to the rear wall l6 of the brush-boxes 4.

Extending transversely, or in a front-and-back direction, depending upon the point of View, are a plurality of spaced transverse walls I! which extend between the rear wall I6 of the brushboxes 4, and the mounting-wall l of the brushholder 3. These transverse walls have plane surfaces lying substantially in the direction of coreinsertion and withdrawal. Each of the transverse walls I! has an upwardly extending portion [8 which is provided with a perforation or hole IS in such manner as to be adapted to receive a common pressure-finger shaft 2| therethrough. In accordance with known casting practice, these holes l9 are produced by breakable carbon cores (not shown) which are inserted in the mould before casting, and which are broken out, upon removal of the casting from the mould. The holes thus produced require no machining, and are made with close enough tolerances to use an unmachined cold-rolled steel shaft 2| for the pressure-fingers 22.

The hollow brushholder casting 3 also has a forwardly extending terminal-pad 23, in the form of a lug or projection which extends forwardly from the front wall 2 3 of the brush-boxes 4. The top surface 25 of this terminal-pad or lug 23 is preferably disposed below the top of the brush-boxes 4, so as to avoid the possibility of a careless placement of a brush-shunt terminal 26 thereon, in such manner that a portion of said brushshunt terminal might project over the top of the brush-box B in a manner which would interfere with the sliding movement of the brush 5 in said brush-box. This terminal-pad 23 has a tapped hole 21 therein, for receiving the terminal-securing bolt 28, said tapped holebeing produced by a tapped steel insert 29, in a manner which has been previously explained.

In addition to the brushholder proper, or casting 3 which has been described in detail, my complete brushholder assembly includes the brushes 5, the shaft 2!, and the pressure-fingers 22, all of which have been mentioned in the course of the description of the brushholder proper. Thefingers 22 are journalled on the shaft 2|, and extend forward in a position to apply pressure to the tops of the brushes 5, in a known manner. These pressure-fingers are provided Withsprings 3|, which are shown as being of the round-wire coil-type, having forwardly extending terminals 32, which are adapted to be adjustably engageable in any one of a plurality of notches 33 which are provided, for that purpose, on the pressure-fingers 22. The springs 31 also have rearwardly extending anchoring-portions 34 which extend under the upper thickened lip-portion 14 of the mounting-wall, engaging in the angle which is provided between the inner surface l5 of the lip and the front surface 35 of the mounting-wall 1.

My brushholder is particularly adapted for gang type holders, having either two or three double holders in one casting. Preferably, the number of transverse walls ll, which are provided in the brushholder, is the same as the number of transverse walls 3! of the brush-boxes 4, this number being three, for a casting having two double brush-boxes, for receiving four brushes 5, whereas, in the case of a brushholder having three double brush-boxes, 'for receiving six brushes 5, there will be four transverse walls I1. These transverse walls thus divide the mountingwall 1 of the brushholder into two or three sideby-side portions, separated by said walls, depending upon the number of side-by-side brush-boxes 4 in the casting. Usually, there will be two mounting-pad portions Ill, formed on the mounting-wall 1.

' The advantages of my new brushholder assemblywillbe made clear by a brief reference to brushholder history. Between the years 1932 and 1942, approximately, the brushholder, made by the assignee of the present invention, corresponding to that which is illustrated in the accompanying drawing, was a cast brushholder, with cast fingers, costing more than double the cost of the hereindescribed brushholder. Between the years 1952 and 1947, approximately, the assignee of the present application made a fabricated brushholder with fabricated fingers, at a total cost which was at first slightly more than the cost of the earlier castrdesign, although this cost was reduced to a somewhat lower figure, after the expenditure of a prohibitive investment in tooling and coststudies. The present design utilizes a casting which is adapted to be made from a permanent mould, designed to use the smallest number of cores, all of which can be inserted and withdrawn into and out of the mould in a single direction and at the same time, so that my present casting is a very great deal cheaper to manufacture than any previous brushholder, either cast or fabricated. I prefer to use, in my new design, a type of fabricated pressure-finger 22 which was developed in connection with the fabricated brushholders previously mentioned.

While I have illustrated my invention in only a single, preferred form of embodiment, it will be obvious that my invention is susceptible of having various changes made therein, in the way of additions, omissions, and substitution of equivalents, without departing from the essential spirit of the invention. I desire, therefore, that the appended claims shall be accorded the broadest construction consistent with their language.

I claim as my invention:

1. A hollow brushholder adapted to be made as a casting from a permanent mould and requiring cores which may all be inserted and withdrawn in one direction at one time, said brushholder being characterized by a plurality of brush-boxes having walls extending substantially in said direction of core-insertion and withdrawal, a mounting-wall having a rear surface at an angle to said direction of core-insertion and withdrawal, said mounting-wall having a thickened mounting-pad portion having a lower inner surface lying in such direction as to admit of said core-insertion and withdrawal, said mountingwall also having an upper thickened lip-portion having an inner surface lying substantially in said direction of core-insertion and withdrawal, and a plurality of spaced transverse walls extending between the rear wall of said brushboxes and said mounting-wall, said transverse walls having plane surfaces lying substantially in said direction of core-insertion and withdrawal, said'transverse walls each having an upwardly extending portion which is perforated in such manner as to be adapted to receive a common pressure-finger shaft therethrough, said thickened mounting-pad portion of the mounting-wall having a tapped hole therein, in combination with said common pressure-finger shaft, a plurality of pressure-fingers journaled on said shaft, and a pressure-finger spring having a rearwardly extending anchoring-portion extending under said upper thickened lip-portion of the mounting-wall.

2. A hollow brushholder adapted to be made as a casting from a permanent mould and requiring cores which may all be inserted and withdrawn in one direction at one time, said brushholder being characterized by a plurality of brush-boxes having walls extending substantially in said direction of core-insertion and withdrawal, a mounting-wall having a rear surface at an angle to said direction of core-insertion and withdrawal, said mounting-wall having a thickened mounting-pad portion having a lower inner surface lying in such direction as to admit of said core-insertion and withdrawal, said mountingwall also having an upper thickened lip-portion having an inner surface lying substantially in said direction of core-insertion and withdrawal, a plurality of spaced transverse walls extending between the rear wall of said brush-boxes and said mounting-wall, said transverse walls having plane surfaces lyingsubstantially in said direction of core-insertion and withdrawal, and a forwardly extending terminal-pad extending forwardly from the front wall of said brush-boxes and having a tapped hole therein adapted for the securing of a brush-shunt terminal, said transverse walls each having an upwardly extending portion which is perforated in such manner as to be adapted to receive a common pressurefinger shaft therethrough, said thickened mounting-pad portion of the mounting-wall having a tapped hole therein, in combination with said common pressure-finger shaft, a plurality of pressure-fingers journaled on said shaft, and a pressure-finger spring having a rearwardly extending anchoring-portion extending under said upper thickened lip-portion of the mountingwall.

GERHARD P. LESSMANN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,936,422 Burnham Nev. 21, 1933 2,423,926 Britton July 15, 1947 FOREIGN PATENTS Number Country Date 133,648 Great Britain Oct. 16, 1919 275,989 Great Britain Mar. 22, 1928 313,267 Great Britain June 13, 1929 

